Question: What is the greatest common factor of $4$ and $5$ ? Another way to say this is: $\operatorname{gcf}(4, 5) = {?}$
Explanation: The greatest common factor is the largest number that is a factor of both $4$ and $5$ The factors of $4$ are $1$ $2$ , and $4$ The factors of $5$ are $1$ and $5$ Thus, the greatest common factor of $4$ and $5$ is $1$. $\operatorname{gcf}(4, 5) = 1$